I've had to disable mypy a couple time for specific parts that it doesn't understand. Very annoying how it breaks on non-trivial stuff because that'd be the use case where you'd want it most.
I've never had it prevent a problem. I like staticly/strongly typed languages for this reason and putting optional type annotations into a language is never going to work out imo.
I upvoted because I had a similar experience; however, your conclusion doesn't follow. Python's borked type checking doesn't mean optional type annotations are fundamentally not going to work out.
In particular, if Python added support for Go-like interfaces and recursive types, it wouldn't fall over for ~99% of nontrivial cases.
I've never had it prevent a problem. I like staticly/strongly typed languages for this reason and putting optional type annotations into a language is never going to work out imo.